\[1 - p - q + pq =\]
\[= (1 - p) - q(1 - p) =\]
\[= (1 - p)(1 - q);\ \]
\[p = 1001;\ \ q = 3,013:\]
\[(1 - 1001)(1 - 3,013) =\]
\[= - 1000 \cdot ( - 2,013) = 2013.\]